Lamb was engaged as an art teacher at the Dublin Metropolitan School of Art in the summer of 1920. That same year, he showed six paintings, including
Peasants of Clare, at the
Gaelic League's Oireachtas exhibition, and he joined with Paul and
Grace Henry,
Letitia Hamilton,
Harry Clarke,
Mainie Jellett, Edward O'Rourke Dickey and
Clare Marsh to form the
Society of Dublin Painters. Their first exhibition was held at the St. Stephen's Green Gallery, Dublin, in August. In 1921, Lamb debuted at the Fortieth Annual Exhibition of Belfast Art Society with five works including
A Lough Neagh Fisherman,
A Northern Cross-road Dance (previously on display at the Royal Hibernian Academy in the spring of 1921), and a portrait of fellow Ulster artist
John Hunter. He exhibited with the Belfast Art Society in two subsequent years, showing four watercolours in 1922 and six oils in 1923. Lamb was profoundly affected by the nationalism arising from the failed
Easter Rising in 1916. Lamb first visited
Carraroe in the Connemara
Gaeltacht in 1921, where he found what he termed the 'National essence'. He returned to Carraroe in 1923 and visited the area frequently thereafter. In 1935 he built a cottage there where he remained until his death. Between 1926 and 1928 he divided his time betwixt a caravan on the
Aran Islands and a house in Brittany. In the following year the Stephen's Green Gallery was once more a venue for a solo exhibition of Lamb's work. He showed around fifty works in total, with the majority "reflecting the light, life and atmosphere of the coast of Brittany", with a few from Connemara. Lamb showed at the same venue annually and in 1932 he displayed a further fifty oils in an exhibition dominated by works from the Gaeltacht, including
A Connemara Woman. Writing of Lamb's 1934 exhibition at the Stephen's Green Gallery the
Irish Times critic commented, "Better than the propagandists and politicians is Charles Lamb, the artist, as an advocate of the attractions of the Gaeltacht." In 1928 Lamb exhibited in Boston for the first time. In each of the following two years he showed in New York, before exhibiting in London in 1931. Lamb was included in an exhibition of modern Irish paintings and lace which travelled to Brussels as part of a trade mission in 1930. Lamb was joined by works from
William Orpen,
John Lavery,
Dermot O'Brien, and
James Humbert Craig. Upon their return to Ireland the paintings were displayed at the premises of the Irish Cottage Industries on
Dawson Street Dublin before being broken up. In October 1930 Lamb was elected an honorary Academician of the Ulster Academy of Arts. Lamb was amongst 540 artists from 31 countries who submitted work as part of the art competitions at the
1932 Summer Olympics in Los Angeles, where he showed
A Galway Fisherman. Amongst his competitors where fellow countrymen
John Lavery, Leo Whelan, Jack B Yeats, and James Humbert Craig. Lamb also competed in the
1948 Summer Olympics at the
Victoria and Albert Museum, with the
Curragh Races, Connemara, where Letitia Hamilton took bronze in the Oil and Water colours event with
Meath Hunt Point-to-Point Races. Lamb built a house in Carraroe in 1935 and also arranged his first annual exhibition and summer school in the same year. Before the outbreak of World War II Lamb spent the winter of 1938 to 1939 in Germany. When the Council for the Encouragement of Music and the Arts was formed in February 1943, Lamb was one of nineteen artists included in a loan exhibition entitled
Living Irish Artists. Lamb was also included in
The Collection of Zoltan Frankl exhibition organised by CEMA at the Belfast Museum and Art Gallery in the following year, which also included paintings by
R O Dunlop and
George Clausen. The CEMA Gallery at Donegall Place, Belfast was the venue for a solo exhibition of Lamb's work in autumn 1947. The artist returned to his birthplace for an exhibition of landscapes and figure painting at his Father's business premises on Bridge Street, Portadown in December 1948. In 1949 Lamb illustrated
Máirtín Ó Cadhain's book
Cre na Cille, Lamb's work was part of a collection sent to Boston and Ottawa by the Cultural Relations Committee in a 1950 exhibition entitled
Contemporary Irish Paintings. In 1951, as part of a national celebration of the
Festival of Britain, fifty of Lamb's work featuring Irish scenes and people were exhibited in Portadown's town hall. Lamb was represented by six oils at the 1954 annual exhibition of the Royal Hibernian Academy, where he showed with fellow Ulster Academicians
William Conor and
Frank McKelvey. == Death and legacy ==